Time Frame

• Fire blight affects the blossoms first, according to the University of California. Blooms may turn brown and wither, and branches may ooze a light brown fluid. Later, the bacteria spreads to the leaves, branches, and trunk, and may eventually kill the tree. The bacteria spreads quickly in warm, rainy conditions, and after hail has damaged the fruit and tree.
  
  

Considerations

• Choosing disease-resistant crabapple varieties is the most effective way to minimize fire blight, according to Colorado State University. Some disease resistant varieties include Hyslop, Mary Potter, Red Jade, and Snowdrift.
  
  

Symptoms

• The symptoms of fire blight include cankers, brown, water-soaked blossoms, and blackened leaves and twigs, according to Colorado State University.
  
  

Prevention/Solution

• Affected branches may be pruned out, preferably in the winter when the tree is dormant. If you prune in the spring or summer, disinfect pruning tools by dipping them in a solution of 9 parts water to 1 part chlorine bleach. Trees may also be sprayed with a copper spray of streptomycin as a preventative measure prior to signs of outbreak. These sprays are ineffective on infected trees.